Mandates to reduce vehicle accidents are motivating remarkable progress in electronic systems that enable cars to avoid crashes, with or without driver intervention. The new RH850/P1x-C Series of single-chip solutions delivers the features and capabilities required for implementing robust functional safety and driving support. In future vehicles, these high-end MCUs will be the in-car control system's brain that makes 'judgments' about the coordination of multiple safety functions.

Linking onboard safety functions together makes vehicles safer

Computerization is expediting the evolution of car safety functions

Cars are becoming increasingly computerized and their safety functions are evolving rapidly:

"Collision damage reduction brake systems" automatically activate brakes when a car rapidly gets too close to the vehicle in front of it. Such systems now are mandatory for new cars sold in EU countries. They not only slow down a car, but also bring it to a stop, if necessary. No driver action is required. This effective safety feature is increasingly affordable and more and more low-priced vehicles offer it.

Conventional cruise control systems recently have grown into Adaptive Cruise Control (ACC) systems. They can maintain a pre-set speed, of course, but—importantly—they do so only when there is no traffic ahead. When a car gets too close behind to a vehicle in the same lane, the ACC slows down the car, causing it to follow the vehicle in front at a constant safe distance. This reduces drivers' fatigue while also improving fuel efficiency.

Lane Departure alarm systems previously just alerted the driver when the car was drifting into another lane. Newly introduced enhanced versions, called Lane Keeping Assist Systems (LKASs), provide a power-assist function that helps the driver turn the steering wheel to maintain lane position. Deliberate changing of lanes requires the driver to override the LKAS.

Decreasing prices expand the market for and spread of innovation

What's significant, yet not too surprising, about the safety advances described above is how relatively quickly they migrated down from luxury cars to mainstream models. That trend is evidenced in numerous other areas, as well.

Automakers now offer more new-car features that promote safer driving. Systems are available that automatically read road signs and provide driving advisories, detect pedestrians and bicyclists, generate warnings if they identify excessive levels of driver fatigue and drowsiness, and more. Consumers can buy such innovations at increasingly reasonable prices (see Figure 1).

Figure1. Safety functions increasingly popular in new cars

Lower prices encourage car buyers to purchase optional safety features and boost vehicle sales. In turn, the rising volumes motivate automakers and their suppliers to invest more R&D money in creating new designs and enhancements. Today this market cycle has gained tremendous momentum as competition rages in the industry.

MCU—the brain of in-vehicle safety functions

Safety functions acquire information through sensors such as radars and cameras. Distance and comparative speed are determined using laser, millimeter-wave and ultrasound-wave radars that measure how long it takes for a transmitted pulse to reach an object and bounce back to a receiver. Infrared ray (IR) cameras are used to detect pedestrians and animals at night, while regular cameras, like those in cellphones, identify road signs and obstacles in daylight. Multiple cameras achieve wrap-around fields of view.

Information from sensors and cameras are sent to and processed by the embedded microcontrollers in the safety system—its brain, so to speak. With minimum delay, these chips have to send appropriate signals to various actuators and the Engine Control Unit (ECU) to ensure safe control of the vehicle. A few milliseconds after a problem is detected, corrective actions are initiated. Threat responses are implemented much faster than drivers can react.

Something falls off the vehicle ahead and a car in the next lane prevents escape!

In complex, dynamic situations, optimum 'judgments' are crucial

Many automotive R&D efforts aimed at decreasing accidents have focused on improving the performance of individual vehicle features such as the ACC, LKAS and automatic braking systems. However, manufacturers in the automotive industry are finding it increasingly necessary to devise solutions for situations that can't be successfully managed by just one vehicle safety function.

Safety threats encountered when driving typically happen unexpectedly and present multiple difficulties, such as when an object falls from the car running in front of you, and there are cars in the adjacent lane (see Figure 2). Successfully preventing or minimizing damage and injury mandates that multiple vehicle safety functions almost instantaneously work in tandem. Developing this capability is the major challenge for automotive system engineers.

Figure2. Coordinating multiple safety functions will be necessary in the future

An enhanced accident-avoidance system has to monitor not just the car ahead, but also everything in its immediate surroundings. Details of the dynamic situation must be determined, especially the speed and positions of cars and trucks that are pacing, passing and approaching, and the car's distance from roadside objects.

Safety systems that can process all of these factors should help prevent contacts with other vehicles and obstacles when the driver turns the steering wheel and/or stomps on the brakes. Accomplishing this demands fast processing for situation analysis, plus precise, coordinated control of actuators.

Executing several corrective actions simultaneously greatly increases the amount of data and computations that the safety system must perform. The best design approach for handling the requisite processing load is to assign the task to a primary processor—a robust high-end automotive safety MCU. This design approach eliminates response delays inherent in distributed processing approaches that use scattered MCUs.